In for example the areas of food processing, pharmaceutical and cosmetics, purity commands are usually of highest priority. Gate valves are often used in such industries for opening and closing different lines.
The valves, after being in contact with one type of liquid or gas, usually need to be thoroughly cleaned before coming into contact with other liquids or gases in order to meet the high sanitary requirements and to avoid contamination by bacteria.
As an example, gate valves generally have some kind of gasket or gaskets which needs to be cleaned at regular intervals. These gaskets may be detached from the gate valve and be completely removed from the gate valve assembly before cleaning. This, however, means that the process has to be stopped and also usually requires manual interaction.
The cleaning is often performed with highly acidic or alkaline solutions to ensure that there is no contamination of bacteria or unwanted products. If for example rubber gaskets are used, these have to be replaced regularly due to degradation or crack formation that may arise in the rubber after repeated exposure to harsh cleaning conditions.
Document U.S. Pat. No. 5,201,490 shows a gate valve-seal assembly comprising a gate valve body inside of which a gate valve seat is formed. The valve is opened and closed by actuating a stem-plug, and a PTFE gasket is used for sealing against the gate valve seat. There is however a need in the art for improved valves for use when the sanitary requirements are of high importance.